GFS2: Test bufdata with buffer locked and gfs2_log_lock held
authorBenjamin Marzinski <bmarzins@redhat.com>
Wed, 7 Nov 2012 06:38:06 +0000 (00:38 -0600)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 17 Jan 2013 16:51:06 +0000 (08:51 -0800)
commit8b564a8e7334a2ce7a691ec7fe21195475ae999f
tree8458ebabdf7c54feb33055a7784a16cbb386ad47
parent74abeffd733e53f83e94fc0d90c0a105af7c58ae
GFS2: Test bufdata with buffer locked and gfs2_log_lock held

commit 96e5d1d3adf56f1c7eeb07258f6a1a0a7ae9c489 upstream.

In gfs2_trans_add_bh(), gfs2 was testing if a there was a bd attached to the
buffer without having the gfs2_log_lock held. It was then assuming it would
stay attached for the rest of the function. However, without either the log
lock being held of the buffer locked, __gfs2_ail_flush() could detach bd at any
time.  This patch moves the locking before the test.  If there isn't a bd
already attached, gfs2 can safely allocate one and attach it before locking.
There is no way that the newly allocated bd could be on the ail list,
and thus no way for __gfs2_ail_flush() to detach it.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/gfs2/lops.c
fs/gfs2/trans.c